The present invention relates in general to small arms and in particular to a new and useful mechanism in an automatic weapon which permits firing of the weapon in either automatic or semi-automatic mode, with an open or a closed bolt.
Automatic weapons are known which include a fire selector which has three positions. The first position is generally a safety which prevents accidental firing of the weapon. The next position is generally a semi-automatic position which permits firing of a single round each time the trigger is depressed. In order to fire again the trigger must be released and pulled again. The fire selector can be placed into its third position for establishing automatic fire wherein the weapon continues to fire one round after the other while the trigger is held. This continues until the trigger is released or until all the ammunition has been expended. Weapons are also known which can operate from a so called closed bolt condition or a so called open bolt condition. A weapon which operates with a closed bolt can only fire when a bolt is seated up against a cartridge in a chamber of the weapon. The cartridge is fired when its primer is struck by a firing pin. This mode of operation is desirable during normal use of a fire arm since accurate aiming is easier due to the lack of large moving masses after the trigger is pulled and the chamber is closed against exterior contamination.
Weapons which use an open bolt include a sear which holds the bolt in a position spaced away from the chamber. Upon pulling the trigger the bolt is released. This generally causes the stripping of a cartridge from a magazine. The cartridge is then pushed into the chamber and immediately ignited by a firing pin. This mode of operation is desirable when firing long continuous bursts that generate substantial amounts of heat. If a barrel is sufficiently heated, it can cause unintentional discharge (cook-off) of a cartridge in the chamber. This mode of operation is generally used in machine guns while a closed bolt mode of operation is generally used in rifles.